Observation of x-ray line emissions are valuable for determining the thermodynamic state of the emitting plasma. For laser produced plasmas, diffraction crystals can be used to isolate x-ray monochromes to obtain high resolution spectral measurements. We will describe a versatile multi-crystal high resolution spectrograph used for photon energies from 0.5 to 6 keV. We will discuss a calculational package that tunes the response and sensitivity of the instrument and estimates the effect of source extent on spectral resolution. A scheme using fine slits to obtain spatial resolution with the basic instrument will also be described. An instrument is being built for Shiva diagnostics that incorporates a diffraction crystal and an x-ray streak camera. The design rationale for the crystal stage will be discussed.

Using double exposure holographic interferometry, an investigation has been made of the Nd laser produced plasmas surrounding disk targets irradiated at different angles of incidence. Measurements have produced a detailed description of the plasma profile necessary for realistic simulations of resonance absorption. A 2660A 15 psec probe pulse is produced by frequency quadrupling a fraction of the main Nd laser pulse from the Janus laser. F/1 and f/10 lenses were utilized to irradiate the targets with intensities ranging from 10/sup 13/ w/cm/sup 2/ to 10/sup 16/ w/cm/sup 2/. Measurements have produced the shape of the electron density profile near critical, the direction of the plasma blowoff, and revealed transverse rippling of the isodensity surfaces.

Objective is to determine the fracture toughness of A533B-1 steel by computer modeling Charpy V-notch tests. A computer model of ductile fracture was developed that predicts fracture initiation. The model contains a set of material-dependent parameters obtained by computer simulations of small specimen tests. The computer calculations give detailed stress and strain histories up to the time of fracture, which are used to determine the model parameter values. The calibrated fracture model, that correctly predicts fracture initiation (and initiation energy) in the Charpy specimen, may then be used to simulate tests of accepted fracture-toughness specimens and hence obtain fracture toughness. The model parameters were calibrated to predict fracture in four different test specimens: two different notched-tension specimens, a simple tension specimen, and a precracked compact-tension specimen. The model was then used in a computer simulation of the Charpy V-notch specimen to initiate and advance a flat fracture. Results were compared with interrupted Charpy tests. Calibration of the model for two additional heat treatments of A533B-1 steel is in progress.

The Environmental Science Division at Lawrence Livermore Laboratory has in use a system of absolute Instrumental Neutron Activation Analysis (INAA). Basically, absolute INAA is dependent upon the absolute measurement of the disintegration rates of the nuclides produced by neutron capture. From such disintegration rate data, the amount of the target element present in the irradiated sample is calculated by dividing the observed disintegration rate for each nuclide by the expected value for the disintegration rate per microgram of the target element that produced the nuclide. In absolute INAA, the expected value for disintegration rate per microgram is calculated from nuclear parameters and from measured values of both thermal and epithermal neutron fluxes which were present during irradiation. Absolute INAA does not depend on the concurrent irradiation of elemental standards but does depend on the values for thermal and epithermal neutron capture cross-sections for the target nuclides. A description of the analytical method is presented.

As part of the effort to extend our x-ray diagnostic capabilities, we have made x-ray spectral measurements of laser-produced plasmas for photon energies down to 100 eV with a time response of 0.5 nsec. Fast, windowless x-ray diodes were used in conjunction with critical angle reflecting mirrors and thin filters for energy definition for two channels, 300 to 600 eV and 800 to 1300 eV. A third channel, using only an x-ray diode and filter, provided spectral information in the 100 to 300 eV region. Results from exploding pusher targets will be presented and compared with those of other diagnostic techniques and Lasnex calculations. Future expansion and modifications of the present system will be discussed.

We discuss the design of filtered detector arrays for single pulsed, 100 keV photon spectral and angular distribution measurements at the Lawrence Livermore Laboratory Argus laser facility.

Plasma generated in low-density vapor by a negative ion beam has been studied experimentally and computationally. We show that space charge neutralization of the beam occurs at very low vapor density, and that correspondingly the electron density may be much less than the beam and plasma ion densities. When there is a large local gas density, as in a charge changing cell, the resulting high electron density is also localized to the same region. Therefore, very few electrons will reach a negative ion accelerator even if it is placed one or two beam diameters from such a cell.

The laser resonance absorption technique has been used to determine the relaxation rate of electronically excited neodymium vapor during its expansion into vacuum. Significant increases of population into ground and 1128 cm/sup -1/ levels were found. Analysis shows that interaction between excited metastable atoms and electrons are much more important for relaxation than atom-atom collisions. The final population of neodymium appears to be frozen at a temperature lower than the surface temperature of melt.

The conditions and the reactions that lead to the realization of chemical equilibrium at interfaces and thus to chemical bonding is discussed with specific attention to the platinum/glass and gold/glass systems. Wetting of the solid by the liquid and formation of an interface are part of the problem. Sessile drop experiments and their interpretation are included. 10 figs, 12 refs. (GHT)

A program of making ''global'' fits to the large amount of experimental equation-of-state data on monatomic metals that has become available in recent years is described. The fits are made within the framework of a phenomenological scaling theory for metallic liquids which incorporates recently discovered general theoretical properties of the EOS of liquids. The theory is expected to be applicable to monatomic metals up to high temperatures (approximately 10 to 100 times the melting temperature, T/sub m/) and at all densities, so long as the metallic bonding does not change character. (GHT)

It was shown that recently published observations of angle- and polarization-dependent absorption of intense laser light are consistent with computer simulations of resonance absorption in a steepened plasma profile, with the addition assumption of a modestly rippled critical surface. About 10 percent absorption seems to be due to mechanisms not addressed in the simulations.

The first laser/plasma studies performed with the Shiva laser system will be two sided irradiations extending the data obtained by other LLL lasers to higher powers. The twenty approximately 1 TW laser pulses will reach the target simultaneously from above and below in nested pentagonal clusters. The upper and lower clusters of ten beams each are radially polarized so that they strike the target in p-polarization and maximize absorption. This geometry introduces laser system isolation problems which will be briefly discussed. The layout and types of target diagnostics will be described and a brief status report on the facility given.

Laser fusion targets are being designed to achieve 100 times liquid hydrogen density using the LLL Argus laser. One method proposed for diagnosing the high density is to seed the D,T fuel with Ar gas and measure the spatial extent of the region emitting the Ar x-rays. A crystal spectrograph has been built to image in 1-D the hydrogen like (3.32 keV) and helium like (3.14 keV) Ar x-rays. The spectrograph was calibrated using an 8 ..mu..m source of Ag L/sub ..beta../ x-rays (3.15 keV) from an x-ray machine.